Influence of the SiO{sub 2} interlayer thickness on the density and polarity of charges in Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks as studied by optical second-harmonic generation
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
By accurately tuning the SiO{sub 2} interlayer thickness the density and polarity of charges in Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks can be controlled. We report on the number density, polarity, and physical location of charges present in the stacks as studied by optical second-harmonic generation (SHG). Depending on the SiO{sub 2} interlayer thickness (1–150 nm) the effective charge density in the Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks ranges from 10{sup 13} to 10{sup 11} cm{sup −2} for both n- and p-type silicon. The polarity of the charges switches from negative to positive around a SiO{sub 2} interlayer thickness of 5–10 nm at which point the effective charge density in the stacks is negligible. This switch in polarity is apparent from spectroscopic, time-dependent, and azimuthal SHG measurements. The observed trends in charge density and polarity can be explained by tunneling of electrons into defect states at the SiO{sub 2}/Al{sub 2}O{sub 3} interface as well as the presence of fixed and bulk charges at the Si/SiO{sub 2} interface and in the SiO{sub 2}, respectively. This charge mechanism appears to hold generally for Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks as similar results were observed for SiO{sub 2} films prepared by various techniques.
- OSTI ID:
- 22275747
- Journal Information:
- Journal of Applied Physics, Vol. 115, Issue 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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